Record (basic) field accesses. Intended for use in Mustache templates.

access-recorder.rb

require 'set'
class AccessRecorder
  attr_reader :accessed

  def initialize
    @accessed = Set.new
  end

  def has_key?(*args) true end
  def [](key)
    @accessed << key
    "{{#{key}}}"
  end
end

example.rb

recorder = AccessRecorder.new

Mustache.render("Hello, {{name}}. Welcome to {{planet}}!", recorder)
recorder.accessed.to_a # => [:name, :planet]